The present invention relates to motor assemblies and more particularly to sealed electric motor assemblies for use in a marine environment.
Gasoline, diesel, and electric powered motors have been used as the means of propulsion for boats and other watercraft for many years. For many applications, electric motors are preferred over combustion engines, such as gasoline and diesel powered engines because they are cleaner and quieter. Electric motors are most often powered by on-board batteries that can be recharged, for example, by connection to a municipal power source or by connection with wind-based generators or solar collectors. Further, such batteries can be charged by “regenerative” means, including by collecting energy from braking, coasting, or the like. Electric motors can also have a reduced impact on the environment because they do not directly emit greenhouse-gases and do not divert fossil fuels from use in other applications. The lack of emissions by electric motors can be particularly desirable in marine applications because of the sensitivity of many marine environments.
Electric motors require electronic circuitry to control, for example, the amount of current provided to the motor, enabling the speed or torque of the motor to be adjusted based on, for example, a user's input. Both such circuitry and electric motors themselves can generate significant amounts of heat which can damage both the electronic circuitry and the motor. Thus, various cooling mechanisms have been incorporated into electric motors and their overall systems. Many motors, including combustion engines use mechanical fans attached to a rotating shaft of the motor. Motors can also use an electric fan detached from the motor. These fans can be axial fans that direct air towards the motor or radial fans that direct the air circumferentially about the axis of the fan in which a fan shroud or housing redirects the air towards the motor. Applications using radial fans often use fan housings to redirect air. When used in marine environments, totally-enclosed, fan-cooled (“TEFC”) motors can be advantageous. TEFC motors are typically AC powered and, thus generate less heat than DC motors, which often require brushes. Accordingly, TEFC motors can include an outer housing that lacks vents or other air passages to the interior for cooling the internal components thereof. Rather, TEFC motors typically rely on a fan for convection cooling of the outer housing, which conducts an adequate amount of heat away from the internal motor components for sufficient cooling. The housings for TEFC motors are typically sealed around the axle or other power take-off component and around any other components that extend through the housing, such as wires or the like. Such a seal can be at least dust-tight or can be splash proof, water resistant, or water-proof, the latter of which allows the motor to be submerged in water up to a predetermined depth.
Some electric motors have the electronic control circuitry mounted within various structures that are configured for attachment onto the housing that surrounds the motor, thus using the motor itself as the support structure for these peripheral components. The motor housings must be custom-made or modified to accommodate attachment of these additional structures. Motors with such circuitry arrangements cannot be easily retrofitted or used in place of housings for current combustion engines due to the different space they utilize. Custom mountings are then be required to accommodate these circuitry arrangements which do not have a configuration that matches that of a combustion engine intended for replacement as these engines often adhere to different standards for their mounting configurations.
Therefore, there exists a need for a motor assembly that uses standard motors and fan housings that can be used in place of fuel-based motors and that provides efficient cooling reliability. There is also a need for a motor assembly that can provide a sealed environment for the associated control circuitry, allowing the assembly to take advantage of the incorporation of a TEFC motor.